Since in a step of photomechanical process, the formation of sharp dot images or line images is required, an image-forming system requires very high contrast photographic characteristics (in particular, gamma of at least 10). Hitherto, for this purpose, a process of processing a lith-type silver halide photographic material comprising a silver chlorobromide emulsion having a silver chloride content of over 50 mol %, and more preferably over 70 mol % with a specific developer called a "lithographic developer" containing only hydroquinone as a developing agent and having a very low free sulfite ion concentration (usually not more than 0.1 mol/liter) has been used. However, since for a lith-type silver halide photographic emulsion, a silver chlorobromide having a high silver chloride content must be used, it is difficult to attain a high sensitivity.
As other processes of obtaining high contrast negative images, there are processes using specific hydrazine derivatives disclosed in U.S. Pat. Nos. 4,168,977, 4,224,401, 4,241,164, 4,269,929, 4,311,781, 4,650,746, etc. According to these processes, by processing a surface latent image-type silver halide photographic material containing a specific hydrazine derivative (generally, an acylphenylhydrazine derivative) as a nucleating agent with a developer having pH of from 11.0 to 12.3, photographic characteristics having a superhigh contrast of gamma over 10 and a high sensitivity are obtained. Since in these processes, a silver bromide emulsion or a silver chlorobromide emulsion having a high silver bromide content can be used, a high sensitivity can be achieved as compared to the case of using lith-type silver halide emulsion.
However, it has been found that the foregoing high contrast image-forming system using the hydrazine derivative has various defects. That is, when the foregoing image-forming system is used, high contrast negative images are obtained but, at the same time, it is accompanied by the formation of pepper (black pepper), which becomes a large problem for a photomechanical process. The pepper in photography means black sesame-like spots occurring in an unexposed area, for example, an area to become an undeveloped area between a dot and a dot. The appearance of the pepper causes the trouble of greatly reducing the commercial value as a photographic light-sensitive material for a photomechanical process. Accordingly, various efforts have been made for the development of a pepper restraining technique, but the improvement in pepper susceptibility is frequently accompanied by the reduction of the sensitivity and gamma. Hence, it has been strongly desired to develop an image forming system capable of obtaining a high sensitivity and high contrast without being accompanied by the appearance of the pepper.
On the other hand, for the purpose of improving photographic performance, the technique of incorporating a certain kind of a quaternary ammonium salt polymer in a silver halide photographic material as a silver halide photographic element is disclosed in JP-A-62-9346, JP-A-62-215949, JP-A-63-13034, JP-A-1-280749, JP-A-2-144533, JP-A-2-308160, JP-A-3-36544, and JP-A-3-38637 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"), European Patents 320,692 and 398,223, U.S. Pat. No. 4,914,018, etc., for static prevention, in JP-A-63-249839, JP-A-2-212834, etc., for the improvement of tone, in JP-A-2-68545 and European Patent 306,246, etc., for the improvement of image sharpness, in JP-B-55-39821 (the term "JP-B" as used herein means an "examined Japanese patent publication"), JP-A-60-122942, JP-A-3-27036, etc., for the improvement of photographic characteristics, and in JP-A-1-150130 for the improvement of the performance and the physical properties.
However, it has never been known that by adding a quaternary ammonium salt polymer to silver halide photographic material and processing the photographic material with a specific developer, the sensitivity is greatly increased and also the contrast is greatly increased, whereby negative images of a very high contrast over 10 in gamma can be obtained.